Refining and purification of metals



Patented may 10, 1932 STATES BEFIN'ING AND PURIFICATION OF INIETALS No Drawing.

This invention relates to the refining and purification of metals.

The object of the invention is to improve the physical characteristics of metals and al- 5 loys by treating the same, while in molten condition, with a salt of permanganic acid. -Such salts are potassium permanganate, sodium permanganate and their equivalents. Manganic compounds, such as K MnO may also be used for said purpose.

A further object of the invention is to increase the resistance of nickel and nickel alloys to tarnish :or corrosion, and to close grain the metal and increase the tensile l5 strength of same.

Manganese and oxides of manganese are known to have been used for the treatment of molten metals. I have found that potassium permanganate acts in a manner entirely 'difm ferent than metalic manganese and the oxides of manganese when incorporated with molten metal. For example, I have found that treatment of nickel silver, while in a molten state, with potassium permanganatein'creases the tensile strength of nickel silver and also increases its resistance to tarnish in a strikingly unexpected manner in contrast to the results obtained by the treatment of the same metal with the oxides of manganese or manganese metal. I am not prepared to state the actual theory of the reaction, but I believe it is due to the liberation of nascent potassium and nascent manganese. I have tried the addition of potash and also potassium alone as a purifier of nickel silver, and have also tried the addition of separate quantities of potassium and manganese, but I have been unable to obtain by the treatment of the metal with such substances the novel results obtained by the use of potassium permanganate. I have also experimented with the various salts and oxides of manganese, other than the permanganates, in'the treatment of metals, and 'I have found that they do not impart to the metal the capacity to resist tarnish or corrosion which is imparted to the metal by the addition of the permanganate.

I prefer to treat the molten metal with the potassium permanganate in the presence of a little carbon. However, the addition of car- Application filed March 14, 1931'. Serial No. 522,789.

bon may be omitted where carbon is present in the crucible or raw materials, as the potassium permanganate under these conditions, when added to a molten metal mixture, acts as a powerful deoxidizer and purifies the metal thoroughly. As there is no water present, the permanganate salt cannot act as an oxidizing agent. It is my belief that the usual oxides of manganese, when added to molten metal, do not break down entirely and that they consequently leave the metal permeated with oxides, whereas the treatment of the molten metal with potassium permanganate in the presence of carbon will have a maximum deoxidizing eflect upon the molten metal and possibly will form complex inner anhydrides. This theory is based upon the exceedingly short time required for the reaction between the molten metal and the permanganate to take place, whereas when other oxides are added to the molten metal, a longer time must elapse before any reaction will take place. I

The following is an example of how my invention may be carried out: 75

A nickel silver alloy was made up by mixing 60 pounds of ingot copper with pounds of nickel and melted ina graphite crucible; When these metals were thoroughly mixed, 20 pounds of zinc were added. Potassium permanganate in the proportion of one per cent. by weight of the metals was then addedv and well mixed with the melt just before the latter was poured into moulds. The time required for the permanganate to act upon the melt was just a few seconds. The metal treated showed an increase of 33% in tensile strength over the same metal not treated with permanganate. It was found that the untreated metal was readily corrodible by weathering, whereas the metal which had been treated with permanganate was highly non-corrosive.

Obviously, the permanganate might be add-' ed to the molten metal while in transit from the furnace to the molds or even after the metal has been poured into the molds.

The following comparative results have been obtained by the treatment of nickel silver with permanganate, manganese dioxide, multaneously with suflicient carbon to p'roand manganese, respectively: duce a deoxidizin reaction.

' v In testimony w ereof I have hereunto set Tensile strength my hand. 3 mm ggg g GEORGE F. DORAN.

Bar form Sheet form Pounds Pounds 1% permenganate..---

55, D00 79, 800 No discoloration. $2; manganese diox- 35,400 65,000 Tarnished.

e. lo 3% metallic manga- 36,999 67,999 Do.

nose.

The quantity of potassium permanganate to beadded to the molten metal is preferably 1 from to 1% of the weight of the metal treated. However, it may be varied from a much smaller amount, say .1 per cent., to a much greater amount, say 5 per cent., as desired. g I 90 My permanganate treatment, when applied to steel, has produced excellent results as to resistance to corrosion and closing of the grain of the metal. M invention is applicable'to steel, iron, and a non-ferrous metals, 95 such as-white metal, etc.

The addition of carbon is not always necessary, since some metals contain carbon as an impurity and melting crucibles often are of a carbonaceous nature. If carbon be added, 39 the amount of same can be varied in proportion to the permanganate, although an excess of it is not harmful.

I claim as my invention: 1. A process of refining molten metal which comprises adding thereto potassium permani0;

ganate and carbon in amount suflicient to pro duce a deoxidizing reaction.

2. A process of scavenging non-ferrous metal which comprises simultaneously adding to the molten metal a small uantity of 106 potassium permanganate and car on.

3. A process of refining nickel-containing non-ferrous metal which consists in adding a to the metal while in melted state a quantity of dry potassium permanganate in the pro- 11o portion of from one-half per cent. to one per cent. of the molten metal and carbon.

4. A process of increasin the tensile strength and resistance to tarnlsh of non-ferrous metal, which consists in addin to the 11;;

metal while in molten condition car on and a dry salt of permanganic acid, and casting the metal immediately thereafter.

5. A process of deoxidizing molten nonvferrous metal, which consists in adding to the la.

metal while in molten state a mixture of potassium permanganate and carbon, the carbon being present in amount suflicient to produce a deoxidizing action.

6. A process of refining nickel silver to 12 increase its tensile strength and its capacity to resist tarnish which consists in adding to same while in a molten state a quantity of potassium permanganate of approximatel one per cent. by weight of metal treated, $1- 

